Hi Lord of Terror. Welcome to the Org!

I'm not sure I understand your problem. What were you "unpacking"? Are you referring to installing M2TW or a mod of the game?

Either way, since you aren't exactly sure what you did, it seems a reinstall of the game is in order.

As for changing your portrait (avatar), click on "Settings" in the upper left corner of any page (to the left of "Log Out"). When the Settings page comes up, look down the left side of the screen for "Edit Avatar" and click on that. That will take you to the Avatar page. You can change your avatar there.